1. Field of the Invention
The present invention relates in general to a voltage-to-temperature value conversion device, more particularly, to a device for converting voltages to temperature values by using a thermistor.
2. Description of the Related Art
In general, thermistors are applied to measure the ambient temperature of electronic apparatus, such as the temperature of the motherboard, CPU, and charging battery etc. In general, the temperature specifications of thermistors are within the range between about -40.degree. C. and +120.degree. C., and the resistance of a thermistor decreases as the temperature increases. The general applications of electronic devices, such as the temperature-control of a refrigerator etc., also use thermistors to measure and control temperature. The thermistor is disposed in electronic apparatus where temperature is to be measured. As the temperature varies, the voltage drop across the thermistor changes to a corresponding value. After taking the voltage, the practical temperature can be obtained by referencing the voltage(resistance)-temperature characteristic curve of the thermistor.
The voltage-temperature characteristic curve of a thermistor is a logarithm-like curve, as depicted in FIG. 2. To fit the curve, a lot of voltage value and temperature value sampling pairs are required. The voltage-temperature characteristic curve of the thermistor is transformed into a voltage-temperature cross-reference table such that the voltage measured from the thermistor can be easily transformed into a corresponding temperature. However, the conventional voltage-temperature cross-reference table is implemented in a one-to-one manner by storing every one of the voltage values and every corresponding temperature value sampled from the voltage-temperature curve into a memory device, such as RAM and ROM. Consequently, the amount of memory required and the fabrication cost are increased.